Export JPanel Graphics to .png or .gif or .jpg

I'm trying to develop some sort of paint using Java.

I have a JComponent that is located inside of a JPanel.

I already can draw lines and rectangles into that JComponent.

Now, how can I export this drawings as an image (png, gif, jpg)?

I tried this:

BufferedImage b = new BufferedImage(1700,1100,BufferedImage.TYPE_INT_RGB);
this.print(getGraphics());
try{ImageIO.write(b,"png",new File("test.png"));}catch (Exception e) {}

But that only creates a .png file all black.

Help!!!

RESOLVED!!!

BufferedImage bi = new BufferedImage(this.getSize().width, this.getSize().height, BufferedImage.TYPE_INT_ARGB); 
Graphics g = bi.createGraphics();
this.paint(g);  //this == JComponent
g.dispose();
try{ImageIO.write(bi,"png",new File("test.png"));}catch (Exception e) {}